There have heretofore been known electronic musical instruments which are constructed to allocate or assign any one of a plurality of tone colors (or timbres) to a tone pitch corresponding to a musical note (scale note) performed by depressing a key on a keyboard or the like and generate a tone of the tone pitch with the assigned tone color. In this connection, there have also been known techniques pertaining to an assigner (key assigner) for assigning which tone colors are to be sounded in response to which key depressions (tone pitches).
Among examples of such techniques is one arranged to provide various tone effects, such as dual, split and solo, by a combination of two assigners (see, for example, Patent Literature 1). According to the technique disclosed in Patent Literature 1, each of the assigners controls which tone color should be sounded with what kind of assignment rule (last-depressed key priority or higher-pitch note priority), and up to how many depressed keys are allowed to be sounded.
Also known is a technique which is arranged to provide a tone effect as if four human players are executing an ensemble performance by assigning, in accordance with the number of simultaneously depressed keys, tones of four performance parts (tone colors) equally to tone pitches of the individual depressed keys and causing the tone-color-assigned tones to be generated or sounded (see, for example, Patent Literature 2). More specifically, according to the technique disclosed in Patent Literature 2, the performance parts have respective priorities (priority ranks) corresponding their tone pitches, and these performance parts are assigned to depressed keys, in a high-tone-pitch to low-tone-pitch direction i.e. in an order from “performance part 1” to “performance part 4”, in such a manner that the number of the performance parts assigned is substantially equal among the depressed keys. For example, when the number of simultaneously depressed keys is one, a tone of a tone pitch corresponding to the one depressed key is generated (sounded) simultaneously in the four performance parts (tone colors). Further, when the number of simultaneously depressed keys is two, a tone of a tone pitch corresponding to one of the depressed keys is generated simultaneously in two of the performance parts (with two tone colors), and a tone of a tone pitch corresponding to the other of the depressed keys is generated simultaneously in the other two of the performance parts (with other two tone colors). Furthermore, when the number of simultaneously depressed keys is four, tones of different tone pitches corresponding to the four depressed keys are generated respectively in the four performance parts (with different tone colors); that is, a tone of a different tone pitch is generated per performance part (with a different tone color).